Since most WordPress themes are responsive, no special changes are needed for mobile devices in most themes. You can modify the layout for mobile devices using media queries (CSS.)
Adding a user code to header.php
You might want to create a mobile page and this page will be loaded for mobile devices. In other words, you might be able to create a separate page for mobile (apart from the default page for PC.) In this case, you can use the wp_is_mobile() function.
For example, you create a page whose name is mobile. You want to redirect to this page for mobile devices. For this purpose, you can place the following code on top of the header.php file.
// For users with mobile devices, the following code will redirect them to http://www.example.com/mobile
<?php
if ( wp_is_mobile() && (is_home() || Is_front_page()) ) {
$url = home_url( 'mobile', 'relative' );
wp_redirect( $url);
exit;
}
?>On the front page or homepage in WordPress, users with mobile devices will be redirected to http://user_site_url/mobile. Of course, you can use header('Location: http://user_site_url/mobile'); instead of wp_redirect. Please refer to this WordPress Codex page for wp_redirect.
The better method: Using the wp_print_scripts hook
For your reference, you can implement this feature without editing WordPress theme file if you use a filter or action such as wp_head. However, the wp_is_mobile() function does not work with the wp_head action. In this case, you can use the wp_print_scripts action. Please refer here for the action wp_print_scripts.
// Redirect to its mobile page when users access the front page or homepage using mobile devices
function deque_my_scripts () {
if (is_home() || is_front_page()) {
$url = home_url( 'mobile', 'relative' );
wp_redirect( $url);
exit;
}
}
if (wp_is_mobile())
{
add_action('wp_print_scripts','deque_my_scripts');
}Like this, you can easily redirect mobile users to its mobile page without any other scripts if you use wp_is_mobile().